Colorado Tick Fever IgG Antibody Test
This blood test measures IgG antibodies against the Colorado tick fever virus in a sample of your blood, helping your healthcare provider determine whether you have been previously infected with this tick-borne illness and have developed lasting immunity.
{"The test identifies IgG antibodies, which develop 2-3 weeks after initial infection","A positive result indicates past infection or immunity to Colorado tick fever","Colorado tick fever is transmitted by Rocky Mountain wood ticks in the western United States","Most cases cause mild symptoms including fever, headache, and muscle aches","The test uses immunofluorescence technology to detect antibodies in your blood"}
Key facts at a glance
- LOINC
- 42895-3
- Short code
- CTFV IgG IFA
- Synonyms
- CTFV IgG Ser Ql IF
- Category
- cardiac
- Sample
- serum
- Container
- Serum Separator Tube (SST) or plain red top tube
- Units
- N/A
- Ref low
- 0
- Ref high
- 1
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Indirect Immunofluorescence Assay (IFA)
- CPT
- 86635
- SNOMED
- 371949004
- Specimen volume
- 1-2 mL of serum
- Stability
- Room temperature: 8 hours; Refrigerated (2-8°C): 72 hours; Frozen (-20°C or below): 2 weeks
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 48–72 hours
- Order
- routine
What is this test?
The Colorado tick fever IgG antibody test is a blood test that looks for specific IgG antibodies in your serum. These antibodies are produced by your immune system in response to a Colorado tick fever virus infection. The test uses a method called immunofluorescence to detect these antibodies. IgG antibodies typically appear 2-3 weeks after you are first infected and can remain in your blood for years, providing long-term immunity.
Why might I need this test?
Your healthcare provider may order this test if you live in or have recently visited areas where Colorado tick fever is common (typically the western United States, especially mountainous regions) and are experiencing symptoms such as fever, severe headache, muscle pain, chills, or fatigue. The test is also used to confirm a previous infection, which can be helpful for diagnosis when the initial infection occurred some time ago.
How is the test performed?
A healthcare professional will draw a small blood sample from a vein in your arm. This sample is then sent to a laboratory where technicians will use immunofluorescence techniques to detect the presence of IgG antibodies against the Colorado tick fever virus. You do not need to fast before this test, and the procedure typically takes only a few minutes.
Reference range
Negative: <1:16 titer; Positive: ≥1:16 titer (indicates past or current infection)N/A
No special preparation required. Inform laboratory of recent travel history or tick exposure.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A positive IgG result indicates that you have been infected with Colorado tick fever virus at some point in the past. This means you have developed immunity to the virus. A negative result suggests you have not been previously infected with Colorado tick fever, though it does not completely rule out current infection if it is very early in the course (before IgG antibodies have developed). In such cases, your doctor may recommend repeat testing after a few weeks or may test for IgM antibodies instead, which appear earlier in infection.
Colorado tick fever is generally a mild, self-limiting illness that resolves within a week or two. However, knowing your immune status can help healthcare providers make accurate diagnoses when patients present with unexplained fever after potential tick exposure in endemic areas.
Frequently asked questions
Is Colorado tick fever the same as Rocky Mountain spotted fever?
How long does it take to get results?
Do I need to prepare for this test?
What are the symptoms of Colorado tick fever?
Where is Colorado tick fever found?
Sources
- 1
- 2
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy